Conventional chair-type automatic massaging apparatuses, an example of which is disclosed in U.S. Pat. No. 4 615 336, have been devised in such a way as to carry out a desired massage on the human back. Such apparatus is conventionally provided, in the backrest of the chair, with a perpendicular screw shaft with freedom of forward and reverse rotation by means of a drive motor. A drive mechanism equipped with a massaging ball or roller is linked in screw fashion to the screw shaft. A massaging movement and a percussion movement is effected by the massaging ball, and the drive mechanism is constructed with freedom of vertical movement.
Further, in recent years, there have also been disclosures concerning apparatuses provided with freely rotatable rollers on the left and right sides, instead of massaging balls, whereby it is possible to effect a rolling massage on the human back, backbone and neighboring regions by continuously raising and lowering these rotating rollers.
Moreover, as shown in FIG. 1, a drive mechanism as used in conventional automatic massaging apparatuses of this type has been constructed in such a way as to effect two different types of operation for the above-mentioned massaging ball by means of forward and reverse rotation of an actuating motor 18 provided in the gearbox 15 in such a way that the two output shafts 16, 17 which are connected to the supporting bar of the massaging ball are respectively appropriately driven. A drive gear 20 is attached to the end of the drive shaft 19 of the actuating motor 18, and 21 is a shaft for transmitting the rotation of a large-diameter gear 22, which intermeshes with the gear 20, in such a way as to turn the main drive shaft 25 via the small-diameter gear 23 attached to its other end. The main drive shaft 25 is provided with a threaded portion 28 at one end in addition to rotatably supporting at its other end, the main drive gear 26. The gear 26 has provided in its center a drum-shaped through-hole 27, and meshes with the small-diameter gear 23. Two subordinate gears 29, 29' with differing diameters and provided in their centers with drum-shaped recessed portions 30 are rotatably supported on the center portion of the main drive shaft 25 in such a way that the respective recessed portions 30 face each other. Further, 31 is a pulley which is linked in screw fashion with the threaded portion 28 and arranged in such a way as to support the main drive shaft elastically, its outer circumference being retained via the balls 32 by a support ring 35 which is supported by a leaf spring 34 attached to a dividing wall 33. Pins 36, 37 are respectively provided on opposite vertical surfaces of the pulley 31. Said pins are arranged in such a way that one pin abuts against one of the drive pins 38, 39 as fixedly provided at opposite ends of the threaded portion 28 of the main drive shaft 25, depending upon the axial position of the main drive shaft 25.
Moreover, 24 is a bearing, 40 is a follower pin provided radially in the main drive shaft 25 in such a way as to be contained in the grooved portions 30 of the subordinate gears 29, 29', 41 is a slidable drive pin abutting in the through-hole 27 of the main drive gear 26, and 42, 42' are output gears provided on the ends of the two output shafts 16, 17 in such a way as to mesh respectively with the subordinate gears 29, 29'.
With the above-mentioned conventional drive mechanisms, although it is possible to carry out different operations with the two different output shafts 16, 17 using the forward and reverse rotation of the actuating motor 18, because the main drive shaft 25 is retained elastically, via the balls 32, by the support 35 which is supported by the leaf spring 34 attached to the dividing wall 33, there are disadvantages such as the creation of more than necessary resistance due to the support 35 which retains the main drive shaft 25, or the possible occurrence of an inability to switch drive between the output shafts 16, 17 due to the creation of a less than necessary resistance, or again the occurrence of noise in the gearbox 15 due to the rotation of each of the subordinate gears 42, 42'.